> On May 15, 2025, at 8:06 PM, Oleg Endo via Gcc <gcc@gcc.gnu.org> wrote:
>
> Hi,
>
> On Thu, 2025-05-15 at 17:41 +0100, Andrew Stubbs wrote:
>> Dear GCC Maintainers and Steering Committee,
>>
>> I'm currently doing a feasibility study and effort estimate for
>> upstreaming the existing ARCv3 out-of-tree port [1].
>>
>> Question: Is there likely to be any objection to adding a new "arc64"
>> port in addition to the existing "arc" port?
>>
>> At this point, I would like to check that the general approach is likely
>> to be accepted at the end of the project. Or, at least not rejected for
>> this most fundamental of reasons.
>>
>> The ARCv3 port has been written as a new backend because it is not just
>> a simple evolution of the ARC architecture and starting afresh made more
>> sense to the developers at the time. I'm aware that there are some
>> precedents for this (sh64, ia64, aarch64), so I think it's probably
>> fine, right?
>>
>
> SH5/SH64 was actually part of the original SH port, not a separate
> standalone port. It made the port more complex and convoluted, but probably
> made sense since the it was backwards compatible with the original SH ISA
> (it was like ARM Thumb -- jump to select between classic SH ISA and new SH5
> ISA, from what I remember).
>
> Best regards,
> Oleg Endo
Also: ia64 is a separate ISA. If you were thinking about x86-64, that's part
of i386 ("ia-32"). Similarly, "mips" is both flavors (and all four ABIs). So
there are several examples in both directions.
paul
